Conventionally, a light-emitting device called a multi-wavelength LED is known as a light-emitting diode (LED) which emits plural kinds of light having different wavelengths (JP-A SHO 49-19783 for example). A multi-wavelength LED which emits short-wavelength visible light beams having different wavelengths includes light-emitting layers emitting light beams having different wavelengths produced from gallium indium nitride (GaYInZN: 0≦Y, Z≦1, Y+Z=1), wherein ratios of indium composition ratios (=Z) differ (JP-ASHO49-19783). For example, the multi-wavelength LED is formed using GaYInZN (0≦Y, Z≦1, Y+Z=1) light-emitting layer in which indium composition ratios are adjusted so that blue, green and red which are three primary colors of light are emitted (JP-A HEI 08-88407 and JP-A HEI 08-88408, for example).
As another multi-wavelength light-emitting device, there is a known laser diode (LD) in which a Group III nitride semiconductor layer including a plurality of Group V elements, such as nitrogen (N), arsenic (As) and antimony (Sb), is used as a light-emitting layer (JP-A HEI 07-07223 for example). Also in the conventional multi-wavelength LD, the light-emitting layer comprises AlSbαAsβNγ (0<α, β, γ<1, α+β+γ=1) having different composition ratios so as to emit laser beams of different wavelengths (JP-A HEI 07-07223 for example).
However, in the conventional multi-wavelength light-emitting device, it is necessary to individually form light-emitting layers that emit light corresponding to wavelengths. Thus, in order to emit three primary colors of light, three kinds of GaYInZN (0≦Y, Z≦1, Y+Z=1) light-emitting layers having different indium composition ratios must be formed individually. This makes the procedure of forming the light-emitting layers complicated.
It is also troublesome to electrically isolate light-emitting layers having different composition ratios from each other using etching means or the like. In the conventional multi-wavelength light-emitting device, it is necessary to provide an ohmic electrode on each of the electrically isolated light-emitting layers. Thus, in order to form the conventional multi-wavelength light-emitting device, extremely troublesome procedures, such as crystal growing procedure for a light-emitting layer and device-forming procedure for forming the light-emitting device must be carried out.
The present invention has been accomplished in view of the problems of the conventional techniques, and the invention provides a multi-wavelength light-emitting device which can easily be formed without using the conventional means for individually providing the light-emitting layers for each of multi-wavelengths. That is, the present invention provides a Group III nitride semiconductor light-emitting device which can easily be formed without need of isolating light-emitting layers and which emits light of multi-wavelength.
The present invention has been accomplished as a result of research for providing the semiconductor light-emitting device.